Philosophers’ volume 15, no. 2 When one door is closed, don’t you know, another is open. Imprint january 2015 — Bob Marley 1. Introduction1 In its simplest form, the epistemic closure principle states that, neces- sarily, if you know that P, and you know that if P then Q, then you also know that Q. Or, at least, you would then be in a position to easily An Open and Shut Case: know Q by simple inference. Modifications to the principle have been proposed in response to various problems, both obvious and techni- cal. But these problems won’t concern us here, so we’ll stick with the simple formulation. Epistemic Closure in the The epistemic closure principle lies at the crossroads of many trends in the theory of knowledge. Many tout it as a linchpin in the most compelling skeptical arguments (e. g. Stroud 1984). Some rely on it to motivate contextualist hypotheses about the semantics of knowledge Manifest Image attributions (DeRose 1995, 2009; Cohen 1999). And others appeal to it in the course of motivating views about the relationship between knowledge and practical interests (e. g. Hawthorne 2004). If epistemic closure fails, then the landscape of contemporary epistemology will need to be reconfigured. 1.1 Two arguments against closure There are two main arguments against the epistemic closure principle. The first argument is that rejecting the closure principle is “the only John Turri way to avoid skepticism” (Dretske 2013: 32, emphasis in the original). Suppose that George is standing in front of an audience waving his University of Waterloo hands around while rehearsing a provocative proof (Moore 1959: ch. 7; see also Stine 1976). The skeptic argues: 1. If George knows that he’s standing up, then he knows that he’s not merely dreaming that he’s standing up. © 2015 John Turri 2. But George doesn’t know that he’s not merely dreaming This work is licensed under a Creative Commons that he’s standing up. Attribution-NonCommercial-NoDerivatives 3.0 License. 1. I dedicate this paper to the memory of Fred Dretske, whose generosity and <www.philosophersimprint.org/015002/> insight were truly inspiring. john turri An Open and Shut Case 3. So George doesn’t know that he’s standing up. epistemic closure prevents skepticism from corroding our knowledge of important day-to-day matters: “We can have most of our cake (the Some anti-skeptics respond: only part worth eating) and eat it too” (Dretske 2013: 33). 1. If George knows that he’s standing up, then he knows that Although this is a way to respond to the skeptic, it is certainly not he’s not merely dreaming that he’s standing up. the only way to do so. For instance, contextualists have argued that their own response to skepticism is better because it not only lets us 2*. And George does know that he’s standing up. count many ordinary knowledge attributions as true, but it also allows 3*. So George knows that he’s not merely dreaming that he’s us to retain the epistemic closure principle (DeRose 1995; Lewis 1996; standing up. Cohen 2013). And there are non-contextualist responses that diagnose the skeptic’s mistake in terms of a subtle modal fallacy (Sosa 1999) or a Despite ending up with radically different conclusions, our skeptic pragmatic confusion about illocutionary force or the norms of speech and anti-skeptic start from the same place, namely, by accepting that if acts (Turri 2010a; Turri 2012; Turri 2014a). George knows that he’s standing up, then he knows that he’s not mere- There is a better argument against the epistemic closure principle ly dreaming. A shared commitment to the epistemic closure principle (traceable in some form to Dretske 1970; see Turri 2014b: §19). If a explains the common starting point of the two arguments. The skeptic propositional attitude is closed under known entailment, then the and anti-skeptic then make different use of that shared conditional following conditional is true: if you have the attitude toward P, and premise. The skeptic relies on the intuition that George can’t know you know that P entails Q, then you also have that same proposi- that he isn’t just dreaming and then concludes that George doesn’t tional attitude toward Q. I regret that I attended a play last night. I know that he’s standing up; the anti-skeptic relies on the intuition that also know that if I attended a play last night, then I existed last night. George knows that he’s standing up and then concludes that George From these two facts does it follow that I regret that I existed last does know that he isn’t merely dreaming. night? Far from it. Regret isn’t closed under known entailment. The Dretske (1970) and Nozick (1981) advocate a dramatically different same is true for other propositional attitudes. Gilmore might be hap- response to the skeptic. They accept that George doesn’t know that he py that his sister’s broken arm is healing quickly, and Gilmore knows isn’t merely dreaming (line 2 of the skeptic’s argument). At the same that if her broken arm is healing quickly, then her arm was broken, time, they accept that George knows that he’s standing up (line 2* of but he’s not happy that her arm was broken. I might be surprised (or the anti-skeptic’s argument). Dretske and Nozick reconcile both of angry, or sad) that James won the competition, and I know that if those things by rejecting line 1 of each argument. That is, they deny James won, then someone won, but I’m not surprised (or angry, or that if George knows that he’s standing up, then George knows that he sad) that someone won. Similar remarks apply to other mental states, isn’t merely dreaming. such as perceiving or remembering. By giving up the epistemic closure principle, we “grant the skeptic Setting knowledge aside so that we don’t beg the question, there a partial victory” (Nozick 1981: 270). Some think that the victory is well isn’t a single propositional attitude that is closed under known entail- earned, because it strikes us as a “suspicious” exercise in “bad faith” ment. (On certain formulations of closure, belief might be an exception to claim that we know that we’re not merely dreaming (Nozick 1981: to this generalization.) But knowledge is a propositional attitude. So, 264). Nevertheless, the victory is only partial, because the failure of absent special considerations to the contrary, it’s likely that knowledge philosophers’ imprint – 2 – vol. 15, no. 2 (january 2015) john turri An Open and Shut Case isn’t closed under known entailment either. Without a special reason violates the epistemic closure principle (2004: 38). Theoretical pro- to do so, we should not treat knowledge differently from its kindred. posals to abandon closure are “revisionary” and suffer from “deep and wide-ranging” “conflict” with our “intuition” (Hawthorne 2004: 36). 1.2 Two arguments for closure In light of all this, closure’s proponents find it “striking” (Hawthorne That brings us to the two main arguments in favor of closure. First, 2004: 36) and “startling” (Fumerton 1987) that “some philosophers closure’s proponents point out that competent deduction from known have gone so far as” to deny the principle and, in the process, “bla- premises is “in general a way of coming to” know one’s conclusion, of tantly violate” such a “basic and extremely plausible intuition” (Steup “extending one’s knowledge” (Williamson 2000: 117; Hawthorne 2004: 2005). They marvel at the “absurdity” of such a proposal — though they 33; Stanley 2005: 18–20, 94). The epistemic closure principle is then do admit that it’s less absurd than “denying the transitivity of the taller glossed as a way of “articulating” this “extremely intuitive idea” about than relation” (Hawthorne 2004: 38; compare Hawthorne 2013: 45). competent deduction (Hawthorne 2004: 33). But this train of thought Related to these claims about ordinary practice and the absurdity is far too hasty. Nothing so strong as a necessarily true generalization of denying closure in the abstract, philosophers have also claimed that is needed to vindicate the general epistemic efficacy of competent de- conjunctive assertions which suggest a violation of closure are “abom- duction. Saving and investing prudently is in general a way of retiring inable” (DeRose 1995). Such conjunctions include ‘She knows that she comfortably, but there are of course exceptions (compare Turri 2010b). has hands, but she doesn’t know that she isn’t a handless brain-in- It seems likely that there is a more modest explanation for the efficacy a-vat’ and ‘He knows that his car is parked in the lot, but he doesn’t of deduction. We should rule out more modest explanations before know that his car hasn’t been stolen.’ reaching for a necessarily true generalization. This rather lavish gloss on ordinary practice and what “we” find Second, and much more commonly, closure’s proponents rely heav- intuitively compelling or conversationally “abominable” has thus ily on the claim that epistemic closure is a defining feature of ordi- far gone unchallenged, even by closure’s opponents (Nozick 1981: nary thought and talk about knowledge — that is, of folk epistemology. 205–206; Dretske 2013: 32). Thus it is widely assumed that closure’s As Barry Stroud puts it, epistemic closure is “just a familiar fact about opponents bear the revisionist’s burden of either explaining away human knowledge, something we all recognize and abide by in our contrary intuitions or showing that their view delivers otherwise un- thought and talk about knowing things”: “anyone who speaks about attainable benefits.